Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already establish readOnly, idempotent, and non-destructive behavior. The description adds a valuable behavioral guarantee beyond annotations: it will not expose token secrets or raw tool arguments, which is important safety context for an agent deciding whether to invoke this tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, front-loaded sentence with no filler. The main capability comes first, and the non-exposure clause adds useful safety context without bloat.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool is simple and annotations cover its safety profile, but the description leaves parameter semantics largely to inference and offers no usage guidance relative to sibling tools. It names the return content well, but an agent would still need to guess what 'scope' and 'windowDays' mean in practice.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description carries the full burden of parameter explanation, but it only loosely references 'recent metered usage' and never explains scope, windowDays, or recentLimit. The enum and numeric bounds are visible in the schema, but the description adds little semantic meaning beyond what the parameter names already imply.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb ('Return') and names a concrete resource: 'MCP-visible credit balance and recent metered usage for the bound actor'. It also adds an explicit non-goal ('without exposing token secrets or raw tool arguments'), which further distinguishes the tool's purpose from broader account or health queries.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context for use—checking one's own metered usage and credit balance—and scopes it to the 'bound actor'. However, it does not name sibling alternatives or explicitly state when not to use this tool, stopping short of the highest bar for usage guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.